1. Field of the Invention
The present invention relates to a digital data recording method and apparatus for recording and/or reproducing digital data and a digital data reproducing apparatus.
2. Description of the Prior Art
A digital recording/reproducing technology has recently been utilized in various field of industry, particularly in a digital audio-video application, and digital video devices of D1 or D2 type have come to be utilized in rotary head systems for business use.
In view of an advance made in high-density recording technology and image compression technology such as MPEG, it has been longed for development of a compact, high performance inexpensive digital video device for home use.
Information data (hereinafter referred to as time codes) representative of position information such as information for use in search of contents recorded on a length of magnetic tape and/or time information in the digital video device of either D1 type or D2 type are standardized as LTC (Linear Time Code) which is recorded by a fixed head and VITC (Vertical Interval Time Code) which is recorded in superimposed fashion with image data.
Since LTCs are recorded by the fixed head in parallel relation to the direction of travel of the length of magnetic recording tape, they can be properly reproduced even during a high speed reproduction. On the other hand, reproduction of VITCs at a high speed is correlated with the length of sync blocks which is a unit of recording of data and can therefore be reproduced at a speed some tens times the normal speed.
The digital video device is discussed in detail in "19-mm type D-1 Cassette-Tape Record" (March, 1986, SMPTE J., 95, 3) and "The Composite Digital Format and its Application" (October, 1987, SMPTE J., 96,10).
However, the LTC of the existing structure requires the use of, in addition to the rotary head for recording audio and video signals which are a main signal, a fixed head dedicated for LTC, resulting in an increase of costs. This also has a problem in that the number of recording areas in the length of magnetic recording tape tends to increase since a linear track is necessitated in the length of magnetic recording tape for accommodating time codes.
With respect to VITC, since the VITCs are recorded superimposed with the image data, they cannot be reproduced at a high speed and, in addition, only the VITC time codes cannot be recorded again.
These problems are extremely detrimental to the existence of the data recording apparatus.